Recently, some portable device has a function to carry out mutual communication easily not via other device. For example, a portable device with the wireless LAN function is widely prevailing. Moreover, it becomes possible to set up an ad hoc network which does not require any access point for a plurality of portable devices. Then, it is possible to exchange data in a near field by many users, each of whom holds a portable device, gathering in the near field.
However, there is a restriction that, in order to set up an ad hoc network, each of devices must exist nearby each other to some extent so that the devices may communicate each other. Moreover, there is another restriction that it is impossible to carry out complicated setting, for example setting for enabling to carryout communication within a group, which is composed of a plurality of people, in a general environment like the internet.
On the other hand, a cellular phone has really little restriction in the communication distance since the cellular phone communicates via a communication base station. Moreover, communication within a group has been already realized as PTT (Push To Talk). While the current PTT function is used for a voice call, actual signals which are sent and received by the cellular phone are digital data which are packet data converted from the voice signal. Therefore, it is easy to carry out data communication by use of the current PTT function. However, since the cellular phone has not a specialized function, for example an advanced data communication function and an advanced data processing function differently from the portable device mentioned above, the cellular phone has limitation in its use.
Here, Japanese Patent Application Laid-Open No. 2004-363998, Japanese Patent Application Laid-Open No. 2005-101716 and Japanese Patent Application Laid-Open No. 2007-259499 disclose an art to enable to carry out communication between communication devices whose communication forms are different each other. Specifically, the system according to the art includes a first wireless communication device which has a function to connect to a mobile communication network, and a second wireless communication device which has not the function to connect to the mobile communication network and has a function to connect to a fixed communication network such as LAN. Moreover, these wireless communication devices set up an ad hoc network each other. That is, each of the wireless communication devices within the ad hoc network has an ad hoc communication function which enables the wireless communication device to communicate each other. In particular, a communication method used in the ad hoc network is the same as one used in the mobile communication network mentioned above.